Electrical musical instrument



May 21, 1940. B. HELBERGER ELECTRICAL MUSICAL INSTRUMENT Filed April 21,1938 3 Sheets-Sheet 1 Amplifier ENTOR ATTORNEYS May 21, 1940. B.HELBERGER ELECTRICAL MUSICAL INSTRUMENT Filed April 21, 1938 3Sheets-Sheet 2 TOR BY 7' V 7 TToRNEYs May 21., '1940. a. HELBERGERELECTRIC AL MUSICAL INSTRUMENT 3 Sheds-Sheet 3 Filed Apt-1141', 1939;

ENTOR Patented May 21, 1940 OFFICE ELECTRICAL MUSICAL INSTRUMENT BrunoHelberger, Frankfort-on-the-Main, Germany Application April 21, 1938,Serial No. 203,241

6 Claims.-

This invention relates to musical instruments and pertains moreparticularly to improvements in electronic musical instruments of thetype illustrated in Lertes and Helberger Patent No. 1,847,119, datedMarch 1, 1932.

It is an object of the invention to provide an improved playing manualby means of which the performer may secure improved musical effects.

Other objects and advantages of the invention will appear hereinafter.

A preferred embodiment of the invention selected for purposes ofillustration is shown in the accompanying drawings, in which:

Figure 1 is a perspective view showing the instrmnent as it may beapplied as an attachment for a piano. 1

Figure 2 is a circuit diagram.

Figure 3 is a top plan view of the playing manual.

Figure 4 is a section on the line 4-4 of Figure 3.

Figure-5 is a section on the line 55 of Figure 3.

Figure 6 is an enlarged perspective view resistance bar.

Figure 7 is an enlarged section on the line 1-4 of Figure 4.

Figure 8 is a section on the line 8--8 of Figure 4.

Figure 9 is an enlarged top plan view of. one of the playing strips.

Figure 10 is a section on the line Ill-I0 of Figure 9.

Figure 11 is a section on the line I IH of Figure 9.

Figure 12 is an enlarged perspective view of one of the end blocks.

Figure 13 is an enlarged perspective view of a playing strip.

Figure 14 is an enlarged perspective view of the supporting stripassembly.

In the musical instrument .disclosed in the prior of the patent referredto, a thermionic tube oscillator is employed, and the pitch of the soundproduced by said oscillator is controlled by varying the frequency ofthe said oscillator by varying the resistance of a circuit includingsaid oscillator. The sai'd'resistance is varied by the performer byoperating the fingers along a playing strip which short circuits more orless of the resistance. In addition, the playing strips were so arrangedthat it was possible for the performer to control the volume of thesound produced by varying the pressure applied to the playing strips bythe fingers. Thus the performer is able to control with a single fingerboth pitch and volume of the sound produced.

According to the present invention all of the advantages of the previousinstrument are retained, and certain improvements are added whichfacilitate the operation of the instrument. Referring to Figure l, theinstrument is illustrated as it may be employed as an attachment to apiano, in order that the performer may be able to use one hand to playon the piano keyboard and the other hand to play on the manual of myinstrument. In this form, as illustrated, the manual designatedgenerally by numeral I may be mounted on the piano keybed, immediatelyin front of the keyboard. It will be understood, however, that themanual may be embodied in a separate instrument if desired.

In the manual illustrated for use as an attachmentfor a piano only twoplaying strips are provided, but it will be understood that as few asone or as many as ten playing strips may be provided depending on thepurpose intended to be served.

The playing strips, designated by numeral 2, are preferably made ofmetal such as brass or stainless steel, and are provided with transverseridges 3 forming frets which indicate to the performer the properplaying intervals. If desired, the upper surface of each playing stripmay be painted with black and white markings, as shown in Figure 3,corresponding to the black and white keys of the piano. This facilitatesthe playing of the instrument by a pianist accustomed to a pianokeyboard. The left end of. the playing strip is firmly anchored bybending it around a fixed strip 4, while the right hand end is tensionedby the leaf spring 5 which holds the strip taut and takes up anyexpansion.

The playing strips are yieldingly supported above the resistance bars 6by means of rubber strips I and sponge rubber cushions 8 of suchconstruction as to provide the desired touch" for the playing strips.For maximum facility in playing it is desirable that when the performerdepresses a playing strip to make contact with the resistance bar, amoderate, but not excessive, finger pressure he required. It is alsodesirable that when the finger is lifted, the playing strip returnquickly to normal position so that rapid successions of notes may beplayed. Finally it is desirable that the playing strips be restrainedagainst transverse movement, or movement above normal playing level.

For these purposes the rubber strips I extend longitudinally parallel tothe playing strips,

strips 1a and 12) being associated with the outer playing strip andstrips 1c and 1d being associated with the inner playing strip. Asillustrated in Figure 7 the opposed flanges 9 and I0 of rubber strips 10and Id lie beneath the playing strip, while the other flanges II and I2lie beneath the flange l3 of the casing and'the flange [4 of the fixedT-shaped bar l5 which separates the two playing strips. Similarly, theflanges l5 and ll of strips Ia and lb lie beneath the playing strip, andthe flange l8 lies beneath the flange IQ of bar I5. In this case,however, the flange is extended outwardly and downwardly to form anapron 2|, which is preferably backed, for stiffness, by a strip 22 ofcanvas or other suitable material. This construction is desirablebecause the outer playing strip is frequently operated by the thumb ofthe performer and the outside panel 23 of the casing must be depressed,as shown, in order not to interfere with proper p y The rubber stripsare each provided with vertical ridges 24 and the edges of the playingstrips fit into grooves 25 formed in the sides of ridges 24. In order toprovide even more positive connection between the playing strips and therubber strips, the playing strips may be provided with ears 25 which fitinto apertures in the rubber strips.

Preferably, the ridges 24 are provided with humps 21, located oppositethe positions on the playing strips corresponding to the black keys of apiano keyboard, in order that these positions may be located by sense oftouch without actually looking at the strips.

Located beneath the rubber strips, and preferably secured thereto arecushion strips 8, preferably made of relatively soft sponge rubber. Ifdesired, the cushion strips may be made even softer by cutting outportions thereof, as at 29. The said cushion strips are supported in U-shaped channels 3|, the upper edges of which serve to limit the downwardmovement of the playing strips. The said channels are supported at theirends in suitable recesses 32 in the end blocks 33, the intermediaterecesses 34 being provided in said blocks to receive and guide the endsof the resistance bars 6.

The construction of the resistance bars is best illustrated in Figure 6.The said bars may be made of any suitable insulating material, but Iprefer to use a relatively soft wood so that the windings of theresistance wire, when applied under tension, may be caused to embedthemselves slightly at the edges of the bar so that they retain theirpositions. If the bar is made of wood, however, I find it advisable tolaminate the bar as illustrated in Figures 6 and 7 to prevent warping.

The method of winding the bar is also illustrated in Figure 6, and itwill be observed that there are groups of windings 35 spaced from andseparated by other groups of windings 36. The individual windings ofeach group 35 are spaced and therefore insulated from one another, butthe windings of groups 36 are in contact and uninsulated. The windingsof groups 35 are of such nature, having regard to number of windings,resistance of wire, etc., that the resistance interposed betweensuccessive groups 35 are such as to provide a tempered scale when theplaying strip is depressed by pressing the flnger against one of thefrets. This is illustrated in Figure 11. In this connection, referringto Figure 2 it will be understood that the effective resistanceinterposed in the line is determined by the extreme left hand point ofcontact between the playing strip and the resistance bar. Thus,referring to Figure 11, and assuming finger pressure applied to fret 3a,there is contact between the playing strip and some of the windings 35aand there is contact with the windings 35a, but there is no contact withthe windings 35b. Since, therefore, the extreme left hand point ofcontact is between the playing strip and the windings 36a, the pitch ofthe sound produced by the oscillator will be the previously determinedtempered pitch for that specific group of windings. It will also beobserved that if now, the performer rolls his finger rapidly to the leftand right of the fret in the manner in which a violinist uses his fingerto obtain a vibrato effect, the performer here may also obtain a vibratoeffect, for in this case the extreme left hand point of contact shiftsacross the windings 36a, alternately to the windings 35a and 35b, thusvarying the resistance sufficiently for the purpose.

It will be noted in Figure 6 that the connecting windings 31 which joingroups 35 with groups 36 are connected thereto at different points asindicated by the soldering points 38. This is done to enable exactpitches to be obtained in the groups 35, the efiective resistance, andhence the pitch, being determined by these connecting points. At thetreble end of the scale it may be desirable to form the windings, ofheavier wire, of low resistance, in order that the number of turns pergroup may be approximately the same throughout the scale.

The upper edge of the resistance bar is preferably rounded as shown, inorder to provide good contact between the playing strip and the windingson the bar. A coating of insulation 40 may be applied to the sides ofthe bar to protect the windings from contact with the adjacent channels,but; the windings along the upper edge of the bar are uninsulated, ofcourse.

As previously explained, the ends of the resistance bar are guided inrecesses 34 in the end blocks 33, but the bar is yieldingly supported byleaf springs 42, 43 and 44. Each of the springs 142 and 44 is providedwith an adjusting screw 45 by means of which the tension of the springmay be adjusted, and the spring 43 is provided with two adjusting screws45 and 41 by which a double adjustment may be effected, one for thefirst part of the downward movement of the bar and the other for thelatter part of such movement.

Immediately below each resistance bar is 10- cated a variable resistanceelement of any known type, that shown herein comprising a block havingembedded therein alternate carbon and steel elements 52 contacted by aspring pressed bar 53 carrying an adjusting screw 54 in contact with thelower edge of the resistance bar. Downward movement of the resistancebar decreases the resistance imposed by element It, so that the greaterthe pressure applied by the performer's finger, the less the resistanceand the greater the volume of tone produced.

In the drawings, certain stops 58 have been illustrated, Figures 1 and3, projecting forwardly from the front panel. The said stops areintended to be used to controlthe quality or timbre of the tonesproduced by controlling a filter interposed between the oscillator andamplifier. In this manner the tones of many well-known instruments maybe simulated, as for example,

violin, clarinet, saxophone, French horn, etc.,

' connections must However, since this mechanism is not claimed in thisapplication, it will not be described herein.

It will be understood that the circuit diagram, Figure 2, shows only oneoscillator 51 and only one playing strip, and that when additionalplaying strips are used, additional oscillators and also be used, all ofthe oscillators being connected to a single amplifier 58 and speaker 59,however.

For purposes of tuning, three variable resistances BI, 62 and 63 areprovided, the resistance 8| serving to adjust the entire scale, whilethe resistance 62 may be used to'adjust the bass end of the scale andthe resistance 63 may be used to adjust the treble end. In this mannervery accurate tuning may be secured. If desired, a knob 64 may bemounted at any convenient part of the instrument, as illustrated, forexample in Figure 1, said knob being connected to control the variableresistance 6!, so that the instrument may be quickly brought into timewith other instruments or with It will be understood that the inventionmay be variously modified and embodied within the scope of the subjoinedclaims.

I claim as my invention:

1. In an electrical musical instrument in combination, a flexiblecontact strip of electricallyconductive material, a rigid bar wound withelectrical resistance material, said bar extending substantiallyparallel to said strip and adapted to be contacted thereby at amultiplicity of different points to provide diflerent effectiveresistances, yielding means supporting said bar and adapted to any pointalong said contact strip, and a variable resistance located between theends ofsaid bar and operated by said movements of said bar.

2. In an electrical musical instrument, in combination, a flexiblecontact strip of electrically conductive material, and cushion meansextending parallel to said contact strip, said cushion an orchestra, forexample.

means being adapted to support said flexible contact strip in normalposition, and to yield to pressure applied to said contact strip by thefingers of the operator.

3. In an electrical musical instrument, in combination, a flexiblecontact stripof electrically conductive material, yielding cushion meansextending parallel to said contact strip, and nonyielding means alsoextending parallel to said contact strip and adapted to limit themovement of said contact strip when pressed by the fingers of theoperator.

4. In an electrical musical instrument, in combination, a flexiblecontact strip of electrically conductive material, cushion meansextending parallel to said contact strip, said cushion means beingadapted to support said flexible contact strip in normal position, andto yield to pressure applied to said contact strip by the fingers of theoperator, and means connecting said contact strip to said cushion means.

5. In an electrical musical instrument, in combination, a flexiblecontact strip of electrically conductive materiaL'parallel cushion meansextending parallel to said contact strip along the edges thereof, saidcushion means being adapted to support said flexible contact strip innormal tions of said contact strips corresponding to the black keys 01'a piano.

BRUNO HEX-BERGER.

